PDA

View Full Version : Faster Clock Speed for Shiftin/out?



achilles03
- 10th December 2005, 16:35
The PBP manual states that the clock speed for shiftin and shift out is about 50kHz, "depending on the oscillator". If I use a 20Mhz crystal, does this increase the clock speed linearly (i.e. assuming a 50kHz clock speed for a common 4Mhz osc, then would the clock speed increase to 250kHz for a 20Mhz xtal?), or does the compiler take the oscillator speed into account (with the define osc X statement) to compensate?

Thanks,
Dave

achilles03
- 13th December 2005, 21:44
I hope the answer to this question isn't unknown. Basically, all I need to know is if the clock frequency using a 20Mhz oscillator is 250kHz, or does it stay at 50kHz (using shiftin/shiftout).

Thanks,
Dave

jbirnsch
- 15th December 2005, 00:41
If you have access to an o-scope or freq counter you should be able to answer your own question.

Jason

Ron Marcus
- 15th December 2005, 02:15
If not, the answer is...yes. It does increase with clock speed.

Ron